Modern gas turbines generally operate at elevated temperatures for extended periods. These elevated temperatures may significantly limit the life of individual components within the gas turbine, thus potentially resulting in costly scheduled and unscheduled outages for the operators. Consequently, thermal and mechanical stresses within the gas turbine, specifically within a hot gas path region of the gas turbine, are critical considerations for gas turbine designers.
During gas turbine operation, a compressor provides a steady source of a compressed working fluid, such as air, that may be channeled to a combustor of the gas turbine, wherein the compressed working fluid may be utilized for cooling various mechanical components within the combustor. In addition, the compressed working fluid may be mixed with a fuel and the mixture ignited in the combustor, thus providing a hot gas that expands rapidly through the combustor and into a turbine section of the gas turbine. The hot gas flows across a series of stationary vanes and rotating blades connected to a rotor shaft, wherein kinetic energy is transferred from the hot gas to one or more stages of the rotating blades, thus turning the rotor shaft and producing work. As a result, the turbine section is exposed to extreme operating temperatures. Existing methods for reducing the temperatures within the turbine section include flowing a cooling medium, such as a portion of the compressed working fluid, through multiple cooling passages located throughout the turbine section. In this manner, the cooling medium generally mixes with the hot gas as the mixture flows from the turbine section to an exhaust outlet of the gas turbine.
In current gas turbine designs, the flow rate of the cooling medium is generally an estimate based on design calculations and gas turbine models. During design validation testing, various gas turbine operating parameters such as pressures and temperatures are measured and compared to the design calculations and models. If the measurements fall within certain limits, the estimated flow rate of the cooling medium is assumed correct. However, it has been observed that the actual cooling medium flow rate of many gas turbines is much higher than assumed, thus resulting in diminished gas turbine efficiency.
Accordingly, a method and a system that determines parameters of a cooling medium, such as the actual flow rate of a cooling medium through the turbine section of a gas turbine, would be welcomed in the technology.